DS00002105A-page 23

USB3450

6.6

Suspend Detection

If a HS device detects SE0 asserted on the bus for more than 3ms (T1), it reverts to FS mode. This enables the FS pull-

up on the DP line in an attempt to assert a continuous FS J state on the bus. The Link must then check LINESTATE for

the J condition. If J is asserted at time T2, then the upstream port is asserting a soft SE0 and the USB is in a J state

indicating a suspend condition. By time T4 the device must be fully suspended.

TABLE 6-4:

RESET TIMING VALUES (HS MODE)

Timing Parameter

Description

Value

HS Reset T0

Bus activity ceases, signaling either a reset or

a SUSPEND.

0 (reference)

T1

Earliest time at which the device may place

itself in FS mode after bus activity stops.

HS Reset T0 + 3. 0ms < T1 < HS Reset T0 +

3.125ms

T2

Link samples LINESTATE. If LINESTATE =

SE0, then the SE0 on the bus is due to a Reset

state. The device now enters the HS Detection

Handshake protocol.

T1 + 100µs < T2 <

T1 + 875µs

FIGURE 6-2:

SUSPEND TIMING BEHAVIOR (HS MODE)

TABLE 6-5:

SUSPEND TIMING VALUES (HS MODE)

Timing Parameter

Description

Value

HS Reset T0

End of last bus activity, signaling either a reset

or a SUSPEND.

0 (reference)

T1

The time at which the device must place itself in

FS mode after bus activity stops.

HS Reset T0 + 3. 0ms < T1 < HS Reset T0

+ 3.125ms

T2

Link samples LINESTATE. If LINESTATE = 'J',

then the initial SE0 on the bus (T0 - T1) had

been due to a Suspend state and the Link

remains in HS mode.

T1 + 100 µs < T2 <

T1 + 875µs

T3

The earliest time where a device can issue

Resume signaling.

HS Reset T0 + 5ms

T4

The latest time that a device must actually be

suspended, drawing no more than the suspend

current from the bus.

HS Reset T0 + 10ms